The invention relates to liposomes which contain multiple branch peptide constructions (MBPCs) for use in the treatment of Human Immunodeficiency Virus (HIV) infections. The presentation of the MBPCs in liposomes substantially increases their activity.
MBPCs are a recent development in the search for a treatment for HIV infections. Essentially an MBPC comprises a core matrix to which are bonded from 2 to 64, and preferably from 4 to 16 peptides. The core matrix is a dendritic polymer which is branched in nature, preferably with each of the branches thereof being identical. The core matrix is based on a core molecule which has at least two functional groups to which molecular branches having terminal functional groups are covalently bonded. Suitable core molecules include ammonia or ethylenediamine. Suitable molecular branches include acrylic ester monomers which are polymerized onto the core molecule. Such molecules may be created to present varying number of branches, depending on the number of monomers branched from the core molecule. The preferred core molecule is lysine. A central lysine residue is bonded to two lysine residues, each through its carboxyl group, to one of the amino groups of the central lysine residue. This provides a molecule with four amino groups, which may be the core matrix for an MBPC having four peptides. Alternatively, one can provide a molecule with eight branches by bonding four lysine residues through their carboxyl groups to one of the amino groups of the lysine residues which are attached to the central lysine. This molecule can serve as the core matrix for an MBPC having eight peptides or can alternatively receive eight lysine residues to form a core matrix for an MBPC having sixteen peptides.
The C-ends of peptides are covalently bonded to each of the branches of the core matrix to form the MBPC. The peptides may be the same, which is preferred, or may be different from one another. The resulting molecule has a cluster of peptides at the surface and an interior core matrix which is not presented and is therefore not but the L amino acids have better activity. Moreover, peptide analogues, synthetic constructs using the carbon skeleton of peptides but omitting the xe2x80x94CONHxe2x80x94 peptide bonds, can be employed in place of peptides. Thus, it should be understood that references to peptides herein may also be taken to include peptide analogues. It is believed that peptide analogues will be more resistant to peptidase and last longer in vivo. If the peptide is too long, the MBPC will become antigenic. It is therefore desirable that each peptide should have not more than ten, and preferably not more than nine, amino acid residues.
MBPCs for use in the treatment of HIV infections were first described by J-M. Sabatier et al in WO 95/07929. The MBPCs described therein have peptides which contain the sequence GPGR (SEQ. ID. NO. 1)(from the V3 loop of the surface envelope glycoprotein gp120 of HIV) preceded by from 0 to 4 amino acid residues and succeeded by from 2 to 4 amino acid residues. The amino acid sequences IGPGR (SEQ. ID. NO. 2) and IXXGPGR (SEQ. ID. NO. 3)(where X is an amino acid residue) are excluded. The most preferred of these MBPCs has a lysine residue core with eight peptides GPGRAF (SEQ. ID. NO. 4) bonded thereto. It may be represented as (GPGRAF)8-(K)4-(K)2-K-xcex2A-OH, the OH terminal indicating the carboxyl group of the xcex2-alanine. That carboxyl group may alternatively be modified to form a carboxamide terminal. This compound is referred to herein as SPC3. These MBPCs and SPC3 in particular have been found to interfere with the virus envelopexe2x80x94cell membrane fusion step and also the infected cell membranexe2x80x94uninfected cell membrane fusion step, either step being thought to be indispensable for cell infection, virus multiplication and the spread of virus in the host organism, by blockading the CD4 receptor present in cells such as lymphocytes and macrophages, possibly by attaching to a membrane co-receptor which is distinct from the CD4 binding receptor, without causing the cell to lose its ability to be activated by other antigens or mitogens.
More recently, in WO 98/29443, J-M Sabatier et al have described further MBPCs which may be effective in the treatment of HIV infection. These use peptides derived from the HIV envelope transmembrane glycoprotein gp41. The peptides contain the sequence RQGY (SEQ. ID. NO. 5) preceded by from 0 to 4 amino acid residues and succeeded by from 2 to 4 amino acid residues. The most preferred of these MBPCs has a lysine residue core with eight peptides RQGYSPL (SEQ. ID. NO. 6) bonded thereto. It may be represented as (RQGYSPL)8-(K)4-(K)2-K-xcex2A-OH, the OH terminal indicating the carboxyl group of the xcex2-alanine. That carboxyl group may alternatively be modified to form a carboxamide terminal. This compound is referred to herein as SPC RL. These MBPCs and SPC RL in particular are also believed to interfere with a critical step of the virusxe2x80x94cell fusion process.
The invention provides liposomes having a sufficient size for while blood cell internalisation, the liposomes containing an MBPC which is useful for the treatment of HIV. Naturally, the preferred MBPCs at present are those disclosed in WO 95/07929 and WO 98/29443, having a lysine core and 8 to 16 peptides incorporating GPGR (SEQ. ID. NO. 1)(but not IGPGR (SEQ. ID. NO. 2) or IXXGPGR) (SEQ. ID. NO. 3) or ROGY (SEQ. ID. NO. 5). Most preferred are those in which the peptides are GPGRAF (SEQ. ID. NO. 4) and RQGYSPL (SEQ. ID. NO. 6), especially SPC3 and SPC RL.
The invention also provides a pharmaceutical composition containing liposomes according to the invention in admixture with a pharmaceutically acceptable carrier. The preferred pharmaceutically acceptable carrier is 0.9% sterile saline, although any suitable carrier for liposome suspension storage and for injection into humans may be used. The pharmaceutical composition according to the invention preferably contains the MBPC in an amount of at least 10 mg/mil so as to keep injection volumes low.
The invention further provides a method for the treatment of a patient having HIV infection, the method comprising administering a pharmaceutical composition according to the invention to the patient by intravenous injection. A likely dosage is from 20 to 100 mg, preferably from 20 to 60 mg of the active ingredient, given at intervals varying from once a day to once a week, according to the viral load. It is anticipated that treatment may not need to be continuous (though it can be), but may be given in courses of from three weeks to one month, then interrupted until the viral load comes up again. Patients would continue to take their current treatment (tritherapies and the like) during and after treatment according to the invention. Because the mode of action of MBPCs makes them independent from viral strain, resistance to the MBPCs should not appear. It should therefore be possible to repeat the treatment, which is currently not possible with RT or protease inhibitors.